Don't even think about it in your furnace. The crucible is not designed for Boro.There is enormous waste that has to be skimmed. Indeed a moly theoretically can do 2750F in terms of heat generated but your refractories will get even with you.

Boro cullet is being melted at 2380. For the most part it's very seedy stuff and not particularly fluid at 2380. It is melted.

I can refer you to the old boro formula for batch from 1915-1925 when it was being trademarked and patented.

It is also expensive as a cullet. There are lots of boro makers who would likely buy the cullet at well over a dollar a lb. Well over. That's where to make your money.